Gas turbine engines (GTEs) produce power by extracting energy from a flow of hot gas produced by combustion of fuel in a stream of compressed air. In general, turbine engines have an upstream air compressor coupled to a downstream turbine with a combustion chamber (“combustor”) in between. Energy is released when a mixture of compressed air and fuel is burned in the combustor. In a typical turbine engine, one or more fuel injectors direct a liquid or gaseous hydrocarbon fuel into the combustor for combustion. The resulting hot gases are directed over blades of the turbine to spin the turbine and produce mechanical power. The engine efficiency can be increased by passing a higher temperature gas into the turbine. However, material properties and cooling limitations limit the turbine inlet temperature.
High performance GTEs include cooling passages and cooling fluid to improve reliability and cycle life of individual components within the GTE. For example, in cooling the turbine section, cooling passages are provided within the turbine blades to direct a cooling fluid therethrough. Conventionally, a portion of the compressed air is bled from the air compressor to cool components such as the turbine blades. The amount of air bled from the air compressor, however, is limited so that a sufficient amount of compressed air is available for engine combustion to perform useful work.
U.S. Pat. No. 8,087,892 to Liang (the '892 patent) describes a turbine blade with a dual serpentine flow cooling circuit. According to the '892 patent, a 5-pass serpentine circuit is located along the leading edge and the tip section of the blade, and a 3-pass serpentine circuit is formed within the 5-pass serpentine circuit with a third leg located along the trailing edge of the blade. In the '892 patent the third leg must provide cooling fluid along the entire trailing edge of the blade, and therefore some of the cooling potential of the cooling fluid passing through the 3-pass serpentine circuit is used for cooling the upper span of the trailing edge, while the hotter, lower span of the trailing edge may be penalized. The turbine blade cooling system of the '892 patent may therefore not provide the most efficient and effective distribution of cooling fluid to the hottest portions of the turbine blade.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.